Marine reverse and reduction gears usually comprise an input shaft, output shaft, and friction clutch between the input and output shafts. The input shaft is connected to a flywheel coupled to a drive shaft of the engine via an elastic coupling (for example, those disclosed in Japanese Unexamined Patent Publication No. 1995-35150 and Specification of U.S. Pat. No. 6,244,964), and the output shaft is connected to a propeller shaft. The output from the engine is transmitted to the propeller shaft via the drive shaft, flywheel, coupling and marine reverse and reduction gear. A marine drive system is composed of these components (for example, Specification of U.S. Pat. No. 4,679,673).
Each component of such a marine drive system is produced by a manufacturer specializing in the field (for example, in the case of a marine reverse and reduction gear, a manufacturer specializing in producing marine reverse and reduction gears). A ship building company then purchases them as parts and assembles the parts into a marine drive system. In some cases, a ship building company purchases an assembled flywheel, coupling, and marine reverse and reduction gear from an engine manufacturer and connects the assembly to a propeller shaft to complete a marine drive system.
However, there are various kinds of propeller shafts, propellers, etc., in the marketplace and they have different torsional vibration state.
Therefore, in prior art techniques, a test working is given after the completion of assembling, and if the torsional vibration of the marine drive system and rattle noise attributable to the torsional vibration are at an unacceptable level, the system has to be disassembled and the parts causing the problem have to be replaced.